2021: Muddling Along To A Healthy Year In Dredging

Calendar picture of a sunny dredging site
Calendar picture of a sunny dredging site

Dear readers, I sincerely wish you all the best for this new year. As things are looking positive on the vaccine front, we should keep testing negative this year. There are lots of items and events to look forward. Last year was not quite what we’ve hoped for and wished each other.

I do hope all of you are OK and are still together with your loved ones. I am fortunately in that respect. So, next to the Covid situation, there were a lot of other noteworthy items. Most of them have been featured here on Discover Dredging. My trip to Bangladesh, just before all the lockdown measures. The graduation of Carsten1 and Omar2 that were completely over Teams. Some attention to our Damen Dredging Experience3. And some other items. Did you enjoy the Donald Duck review?4

Opening scene of ‘Muddy Fine Business’ or ‘Success Test’ (Credit: Disney)
Opening scene of ‘Muddy Fine Business’ or ‘Success Test’ (Credit: Disney)

One sad event was, the last issue of Dredging and Port Construction5. We’ve had to say goodbye to our trusted DPC. Although by now, there has been a kind of digital revival on the CEDA Website6. They opened up a section for Industry News, edited by Namrata Nadkarni. It stands out from the other online media covering dredging as there has been some attention to smaller topics, that would normally not get covered. As I think it is a good initiative, I urge you to subscribe and also participate by sending them any noteworthy news items for publication. Not specifically the usual company press releases, but also the more thought provocative opinions and perspectives on the activities of our dredging community. Active participation could make this CEDA Industry News flourish this year.

Announcement of the CEDA Industry News section (Credit:CEDA)
Announcement of the CEDA Industry News section (Credit:CEDA)

Further personal activities within CEDA are the Dredging Management Commission7 and I am looking forward to the exciting new concept for the CEDA Dredging Days8. Will you participate? Also, I already took the course on ‘Dredging for Sustainable Infrastructure’9, but you should keep an eye out on the next instalment, coming soon10.

A continuation from last year on my Discover Dredging will be some more articles on our Damen Dredging Experience. There are still some exhibit left to review and teaser:… There are some new exhibits arriving! Hope to have that covered when the pandemic will fizzle out we can show you around through our museum. And I hope to continue on pump and dredge technology.

Overview of the Damen Dredging Experience
Overview of the Damen Dredging Experience

Currently, there are some students working on their graduation thesis. Their very interesting topics will be highlighted here as well. Some others will start soon. When you are looking for a fun place to have your internship our your graduation, you might consider a visit to our career page11 or contacting Frank Bosman for any opportunities. Although most positions are filled at the moment, later this year we would welcome fresh brains again.

As our offices will be closed for regular work, I will be working from home most of the time. Probably most of you will do likewise. To keep track of the passage of time over the days, you should have a calendar. As a special service to my audience, I was granted the use of a set of beautiful pictures to create a calendar. You can download the file here and with some DIY skills you should have some original wall decoration for this year.

Stay healthy and stay safe. Hope to see you later this year.

Selection of calendar pictures
Selection of calendar pictures

References

  1. Graduation Of Carsten Markus: Designing And Casting Of Impellers, Discover Dredging
  2. Graduation Omar Karam: Rock Cutting The Egyptian Way, Discover Dredging
  3. Selected articles on the Damen Dredging Experience, Discover Dredging
  4. Book Review: Donald Duck A Muddy Fine Business; Artistic Equipment Design; Discover Dredging
  5. The Last Dredging And Port Construction Magazine, The End Of An Era; Discover Dredging
  6. Debut of CEDA Industry News section and monthly newsletter, CEDA
  7. Selected articles on the CEDA Dredging Management Commission, Discover Dredging
  8. Call for Papers for CEDA Dredging Days 2021 issued, CEDA
  9. Book Review: Dredging For Sustainable Infrastructure, Discover Dredging
  10. 2nd Online Course Dredging for Sustainable Infrastructure planned for March 2021!, IADC
  11. Welcome to the best years of your life, Damen

See also

Increase Your Dredging Knowledge At The End Of The Discharge Line

Keeping watch at the end of the discharge pipe line
Keeping watch at the end of the discharge pipe line

Solving something at the end of the pipe is usually a less desired approach. However, in dredging, it is the place where the valuable stuff is delivered, it might be a good place to start monitoring your process. Let me explain this to you by going back to latest discussed exhibit at the Damen Dredging Experience1.

Pump power exhibit at the Damen Dredging Experience
Pump power exhibit at the Damen Dredging Experience

You might have observed in the pictures of the pump power exhibit, that the velocity of the water flow is indicated by the parabolas of the trajectory. The arc of water is bound by gravity and obeys this trajectory always; independent of the density of the mixture. The two equations of motion can be combined, where the time parameter falls away and the height for a certain distance is only depending on the initial horizontal velocity2. As such, it is fairly accurate indication of the pipe flow. The calculation is universally applicable on earth and the results can be presented in a very simple graph to take with you. Every parabola is labelled with the corresponding horizontal velocity.

Nomogram to find end of pipe velocity
Nomogram to find end of pipe velocity

The above example is a straightforward method to measure the mixture velocity. The US Geological Survey even extended this approach as a standard method to measure the production of wells3. The resulting nomogram has a slightly different layout, as it is intended for finding the production instead of the velocity. For production planning, this will be useful. For monitoring your dredging process, the velocity might be more important. Both approaches of this elegant method do have the benefit, that there is no obstruction needed as in the case of an orifice measurement4.

Nomogram to find the end of pipe production
Nomogram to find the end of pipe production

There is an unconfirmed anecdote that my old professor de Koning started his career as a velocity measurer. In the old days, when he was working as a twelve year old boy with the dredging company of his father. He was assigned to keep watch at the end of the pipe and monitor the mixture pouring out. He had a simple beam with a plumb bob. The beam was moved along the top of the pipe, until the plumb bob was touching the arc of mixture. On the beam were two markings. When the beam was moved in and passed the first mark, the mixture velocity was too low and a red warning flag had to be displayed. If the beam had to move out and the mixture velocity was too high at the second mark, a green flag had to be flown. There was also another white flag, in case only water came on the reclamation area. With this very simple setup, the dredge master could check through his binoculars what the state of the dredging process was.

Working principle and explanation of end of pipe meter
Working principle and explanation of end of pipe meter

They were clever in those days. But the physics still apply. So, even today, one might have a situation, where there is no electronic velocity measurement available (broken, not supplied, not (yet) purchased) and you have to push the limits of the operating envelope of the dredging process. Then, there is probably always somebody around that might be appointed volunteer to be head of the velocity measurement crew. Who knows, he might have a bright future in the dredging academia.

Professor de Koning of the dredging chair at the TU Delft (1981-1993)
Professor de Koning of the dredging chair at the TU Delft (1981-1993)

References

  1. Presenting Pump Power Peculiarities, Playing With Pumps And Pipes, Discover Dredging
  2. Projectile motion, Wikipedia
  3. Estimating discharge from a pumped well by use of the trajectory free-fall or jet-flow method, US Geological Survey
  4. ISO 5167 Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full, ISO

See also

Presenting Pump Power Peculiarities, Playing With Pumps And Pipes

Pump power exhibit at the Damen Dredging Experience
Pump power exhibit at the Damen Dredging Experience

Hej kära läsare, jag vill ta dig till ett land långt borta, för länge sedan. Min älskade Sverige.

In 1996, I started my graduation with Skanska1 in Sweden. They had a project to clean up a lake2 with an auger dredge. The auger was not performing and they asked the Delft University of Technology to investigate the problem and write a report with my solution. Off, I went to Växjö and spent a year on a dredge. During my reconnaissance of the project in the first week, I noticed that the flow in the pipe line was very slow and the motor was hardly working at full speed. As an innocent student, I asked where they were pumping the material to. ‘Oh, through 7 kilometre of pipe and 30 meter up into the hills.’ They were lucky it was such a fluid material and did not settle at such a low velocity. I then proposed they should buy a booster station to increase production3, as I could not see anything wrong with the auger. ‘No, no. It has to be the auger and the engine is strong enough; you see, there is no power required.’

Clean up project at Södra Bergundasjön near Växjö
Clean up project at Södra Bergundasjön near Växjö

That was the first time I saw the slow flow fallacy at work. Intuitively you would expect, that a long pipeline would require more power to transport the mixture than a short pipe line. This is exactly what this exhibit is trying to visualise. Water can be pumped through either the short or long pipe. From the lines on the tank wall, you can read that the output velocity of the fluid is about 1.5 m/s. In the vertical pipe, the delivery pressure is indicated. Multiplying pipe velocity and fluid pressure results in the actual power in the pipe line. The pump has to provide this power, by converting electrical power to mechanical power and eventually fluid power. On the display at the left of the buttons, the consumed electrical power can be read.

Discharge capacity through the short pipe line
Discharge capacity through the short pipe line

When you select the short pipe line, you have to notice the higher flow velocity and the required power at the display. Switching over to the longer pipeline, you will notice a drop in velocity. Due to the longer pipe, the fluid experiences more resistance. For the same pressure, the flow will be lower. Consequently, the power consumption will be lower also! This is exactly according to the theory. A pump at a lower capacity will consume less power, even if the pressure rises slightly.

Discharge capacity through the long pipe line
Discharge capacity through the long pipe line

Off course, the delivered mixture will be less, on the longer line. You might increase the speed of the pump to have more pressure. And indeed, that would require more power. But there is a maximum speed on the pump drive. Same for a very short pipe. You might end up below the idle speed of the diesel engine. Be careful in your project layout that you do take into account this viable operating range for the length of the pipe line. A longer pipeline might require a booster station for increased production. Conversely, a shorter pipe line might be chosen with a smaller diameter for increased resistance and lower power consumption, while keeping the operating point of the dredge pump near the Best Efficiency Point.

Graphical explanation of the power consumption for identical pump speeds
Graphical explanation of the power consumption for identical pump speeds

And the Swedish dredge on 7 km of pipeline? It turned out, it was not a technical problem. They had no hurry. The contractor was hired per week on an open contract…

Auger dredge 'Detritus'
Auger dredge ‘Detritus’

References

  1. Welcome to Skanska, Skanska
  2. Södra Bergundasjön, Wikipedia (Swedish)
  3. Damen booster station, Damen

See also